Yr Wyddfa is the highest ground in Wales, and nearly everything people climb it for was cut by ice. The mountain stands 1,085 metres up in Eryri, in the north of the country. Glaciers bit two bowls out of its flank, one holding the long sheet of Llyn Llydaw, a smaller and higher one holding Glaslyn. What was left between and around them is a horseshoe of ridges pared down to blades. From the lakes on the road in from Capel Curig you have the ring entire — Crib Goch, the summit, Y Lliwedd — and on a still morning the water gives you a second copy. The Pyg Track takes you along the wall of the cwm to the view the mountain is known for: Glaslyn's deep blue directly beneath, Llydaw behind it, and the ruined buildings of a copper mine on the shore between.
Crib Goch is the serious way onto all this, an arête of red rock where you move on hands and feet with the ground gone on both sides. It is a scramble rather than a walk, and rescue teams are on it every year. At the other extreme, carriages have been pushed up a toothed rail from Llanberis since 1896, 7.6 kilometres of it, the only public rack railway in Britain. Walkers on the path alongside keep pace with it for stretches. The cairn at the top is said to cover Rhita, a giant who wore a cloak stitched from the beards of kings he had beaten and who asked Arthur for his. Gwyddfa Rhita, the tomb of Rhita, wore down into the mountain's name. On calm mornings in autumn and winter the cloud settles in the valleys instead of on the peaks, and climbing out of the murk leaves the summits of Eryri standing around you like islands. Winter turns the pyramid white above a frozen Glaslyn. And in June, on a few high ledges the sheep cannot reach, the Snowdon lily opens a single white flower: an arctic-alpine plant stranded here when the ice pulled back, and found nowhere else in Britain.